In Thomason patents, such as U.S. Pat. No. 3,145,707 and 3,215,134, the low-cost open-flow (trickle-flow) collector yielded simple, low-cost solar heat collection. Quality was improved and high efficiency was achieved in the solar heat collector panel of Thomason U.S. Pat. No. 3,989,031, tested at the University of Virginia by Dr. J. Taylor Beard, et al., under a Federal Government contract from ERDA. However, improvement was needed as to the liquid outlet from the collector panel. The present invention helps improve the open-flow (trickle-flow) Thomason solar collector panel.